This morning I ssh'ed into the machine and did upgrade it to 10.10. When it finaly resarted it says something about running in low quality graphics and eventually returned to a command line login prompt. I ssh'ed in again and did a sudo reboot now. When it came back on this time the image is rapidly scrolling from the top to the bottom of the screen. I guess the installed driver doesn't quite work with the S-Video port on which the TV is connected.

previously it was working right with the nvidia proprietary drivers. How can I install thoses without using the GUI tool that comes with Ubuntu?

jockey is the tool used in Ubuntu to manage 3rd party drivers, particularly proprietary ones like the Nvidia drivers. In addition to the gui tool, it has a text based utility for manipulating drivers as well, jockey-text from the jockey-common package. To list what drivers jockey thinks are available for your hardware use jockey-text --list; e.g.: